How to Calculate Percentage Increase
Understand percentage increases and decreases step by step.
Published by QuickUtilaUpdated 2 min read
Percentage increase tells you how much a value has grown compared with where it started. It is used for price rises, salary changes, population growth, website traffic and almost any “how much has this changed?” question.
The percentage increase formula
Subtract the original value from the new value, divide the result by the original value, then multiply by 100.
- 1Difference: 100 − 80 = 20
- 2Divide by the original: 20 ÷ 80 = 0.25
- 3Multiply by 100: 0.25 × 100 = 25
Therefore: The price increased by 25%.
Calculating a percentage decrease
The same formula works for decreases. When the new value is smaller, the result is negative, and the negative sign tells you it is a decrease.
- 1Difference: 200 − 250 = −50
- 2Divide by the original: −50 ÷ 250 = −0.2
- 3Multiply by 100: −0.2 × 100 = −20
Therefore: Costs decreased by 20%.
Why the original value matters
Percentage change is always measured against the starting point. Going from 80 to 100 is a 25% increase, but going from 100 back to 80 is only a 20% decrease — the same difference of 20 is compared with a different starting value.
This is also why the original value can’t be zero. Dividing by zero is undefined, so there is no meaningful percentage increase from 0 to anything.
Increases of more than 100%
A value that doubles has increased by 100%, not 200%. From 50 to 150 is ((150 − 50) ÷ 50) × 100 = 200%, which means the value is now three times the original.
| Change | Percentage change | New value is… |
|---|---|---|
| 50 → 75 | +50% | 1.5× the original |
| 50 → 100 | +100% | 2× the original |
| 50 → 150 | +200% | 3× the original |
| 50 → 25 | −50% | 0.5× the original |
Percentage change vs percentage difference
Use percentage change when one value clearly comes first — before and after, old and new. When two values have equal standing, such as the price of the same item in two shops, use percentage difference instead.